DEEPRESEQUENCING (DR) PLATFORM (BUDGET ONP. 21) The DR Platform will be devoted to more systematic analyses of sequence variation in genes that emerge as likely determinants of interindividual variability in drug response based on some combination of evidence for a role in a drug pathway, phenotype/genotype association, linkage analysis, and differential expression. These genes will arise from the studies performed in Steps 1 and 2, and the analyses carried out in this platform will be preliminary to the large-scale clinical studies planned in Step 3. The goal of this Platform is to obtain a more thorough characterization of the patterns of variation, with a special focus on identifying and understanding the patterns of functional variation in coding and noncoding regions, which in turn will inform the design of subsequent association and functional studies. Examples of how DR data on UGT1A and CYP3A genes will be used to design association and/or functional studies are provided in the CRC (p. 256) and CYP3A (p. 262) Projects, respectively.